ERA5 reanalysis data, station precipitation data from the China Meteorological Administration, NOAA monthly average sea surface temperature (SST) and outgoing longwave radiation (OLR) data from 1980 to 2020 are used in this study to analyze the impact of the zonal position of the East Asian subtropical jet (EASJ) on summer precipitation in China, as well as its response to SST in the tropical central-eastern Pacific. The results indicate that in EASJ westward-shift years (WYs), upper-level convergence and lower-level divergence dominate over the Yangtze River Valley (YRV). The eastward displacement and weakening of the western Pacific subtropical high at 500 hPa is unfavorable for moisture transport to the YRV, leading to reduced precipitation. Meanwhile, upper-level divergence over the Hexi Corridor (HC) promotes rising motion, accompanied by lower-level moisture convergence, increasing precipitation in HC. In EASJ eastward-shift years (EYs), the WPSH strengthens and shifts westward. The convergence and divergence patterns in both upper and lower troposphere, along with moisture conditions and vertical motion in these two regions, exhibit reversed characteristics compared to those in WYs. As a result, precipitation anomalies display an opposite phase distribution relative to WYs. The zonal position of the EASJ is closely related to the summer SST in the tropical central-eastern Pacific. Negative (positive) SST anomalies in this region directly cool (warm) the atmosphere, suppressing (enhancing) local convective activity. These alterations modulate the Walker circulation and lead to anomalous ascending (descending) motion in the tropical western Pacific. The vertical motion anomalies further affect the mid-latitude region of East Asia through the meridional circulation, reducing (intensifying) convective activity near 30°N. Consequently, the meridional temperature gradient in the eastern part of the climatological jet region decreases (increases) due to the diabatic heating, which weakens (strengthens) the tropospheric westerlies and results in an anomalous westward (eastward) EASJ.